Metacarpal and proximal phalangeal fractures are commonly encountered in hand fractures. The majority of these fractures can be treated non-operatively with good functional outcome. However, some unstable fractures with shortening or rotational deformities will require surgical intervention.
For all metacarpal fractures, proper fixation has always been the most important means for proper healing. There are many different types of fixation methods which are mainly in two categories—external and internal fixations. External fixation, usually by means of splints or casts, is used in cases in which the bone pieces are lined up well and surgery may not be necessary. However, some more complicated cases require operative treatment with insertion of an implant to fix the fracture. Ideally, a good internal fixation should have the merits of least exposure, least damage to soft tissue, and ease of manipulation.
There are generally four internal fixation methods currently used by clinicians for metacarpal fractures. They are Kirsches-wire (K wire) fixation, screw fixation, plate fixation, and pin fixation. Though these fixation methods have their own merits in dealing with different type of fractures, they have various shortcomings when applied to hand metacarpal fractures. Advantages of using K wires include minimal exposure and penetration of bone, short hospital stay, early mobilization, and few complications. However, it has the disadvantage of relatively weak fixation. Screw fixation can provide rigid compression loading of fracture site, but greater exposure is required for drilling. Plate fixation is designed to provide rigid internal fixation in order to facilitate early motion and thereby minimise joint and tendon complications. However the technique is demanding and secondary procedures are frequently required. A pin fixation is the insertion of a fixation pin into the medullary canal of a fractured metacarpal for stable bone fixation. The frequent complication rates emphasize the need for meticulous pin placement, adequate intraoperative evaluation of pin position, and satisfactory patient compliance.
So far there is no simple, reliable, effective and less invasive method for the fixation of metacarpal fractures although various types of devices have been developed to address some of the applications. An example of internal fixation by means of intramedullary implant for the fixation of fractured bones is U.S. Pat. No. 6,273,892B1 (Orbay et al.). This relates to an improved method and a related system for fixation of fractures of relatively small bones. It was particularly targeted at metacarpal fractures. Due to its location, splinting and casting it failed to maintain proper fracture reduction. Although the device provided fixation by insertion of fixation pins into the medullary canal of a fractured metacarpal, the effectiveness is limited by its weak torsional and longitudinal stabilities. In most cases, more than one fixation pin is required.
U.S. Pat. No. 6,533,788 B1 (Orbay) relates to a locking device and method for fixation pin stabilization within a fractured bone. This locking device includes a locking sleeve and a handle. This invention produces a device that provides torsional and longitudinal stability to the fixation pin and thereby to the bone through which the fixation pin extends. However, because this invention still adopts the idea of using a fixation pin for the intramedullary stabilization, it has relatively weak fixation, especially in the distal end of the pin where there is no locking device. In addition, other disadvantages such as, for example, frequent complication rates, the need for meticulous pin placement, adequate intraoperative evaluation of pin position, and patient compliance still remain.
Thus, there remains a need and desire for a bone fixation assembly that permits strong torsional and longitudinal fixation stability yet at the same time is less invasive, easy to manipulate, and flexible in application.